The present invention pertains to a velocity diffuser that is employed in a conduit conducting a flow of liquid to increase the velocity and decrease the pressure of an annular layer of the liquid flow adjacent the interior surface of the conduit while decreasing the velocity and increasing the pressure of a remaining portion of the liquid flow within the annular layer.
In lengths of conduit containing a butterfly valve for controlling a flow of liquid therethrough, frequently a flow of liquid of significant velocity will impinge upon the disc of the valve when in its open position, causing the disc to shake. Additionally, a liquid flow of significant velocity bypassing an open butterfly valve can become turbulent, creating cavitation in the liquid flow downstream of the valve. The cavitation can have the undesirable effect of accelerating the wear on the interior surface of the conduit downstream of the valve. Additionally, the shaking of the butterfly valve disc in combination with the cavitation produced downstream of the valve can produce a significant amount of damage to the operating mechanism and external noise.
It is an object of the present invention to provide a liquid flow velocity diffuser that produces a velocity gradient symmetric to the center axis of the conduit with faster flowing liquid in an annular layer adjacent the conduit interior surface and surrounding slower flowing liquid within the annular layer. By producing such a velocity gradient in the flowing liquid, the apparatus of the invention reduces the speed of the liquid impinging on the disc of the open butterfly valve and thereby reduces the shaking and vibration of the valve mountings in the conduit and also reduces the turbulence and resulting cavitation downstream of the valve. As a result, the noise outside the conduit due to the liquid flow past the open butterfly valve is significantly reduced.